The present invention relates to a thermal equalizing system for use within a hot runner system of a plastic injection molding apparatus for maintaining a constant internal temperature within the apparatus. More particularly, the thermal equalizing system employs at least one thermal fluid circulating circuit which uses a heat transfer fluid to remove excess heat from overheated areas within the injection molding apparatus and/or to add heat to under heated areas within the injection molding apparatus.
In operating an injection molding apparatus, it is a common problem that the internal components of the molding apparatus usually require precise and equal temperatures throughout. But typically, the internal components of the molding apparatus develop a temperature differential between different areas of the same component. This is due to inequalities in the heat input and heat output (losses) in various areas of the same component.
One attempt to solve the foregoing problem involves retrofitting such injection molding apparatus with external circulating pumps and/or external fluid heaters for circulating isothermal fluids within channels added to the molding apparatus for that purpose. Such retrofitting has proven to be cumbersome, expensive to implement, and impossible in situations where space is limited. One such example is a hot runner system of an injection molding apparatus, where space and cost limitations make the use of external circulating systems impractical to implement. Accordingly, there remains a need for a thermal equalizing system having an internal circulating fluid for maintaining a constant temperature within the internal components of the molding apparatus, without using means (pumps, heaters, and the like) external to the molding apparatus as previously described.
In the foregoing circumstances, it is an object of the present invention to provide a thermal equalizing system that is compact, self-contained, and creating an adiabatic cycle (a thermodynamic process occurring without the gain or loss of temperature) for producing a constant and equal temperature within the internal components of the molding apparatus.
Another object of the present invention is to provide a thermal equalizing system having a circulating thermal fluid circuit which is self-contained within one or more of the internal components of the molding apparatus, whereby a circulating heat transfer fluid is utilized to remove excess heat from overheated areas and to add heat to under heated areas in a cost effective and economical manner.